Balancing Equations

Conservation of Matter:
Matter (atoms) cannot be created or destroyed. 

Whatever you have at the beginning, you'll still have at the end. 
This means that if there are 2 Al's at the end, you must have had 2 at the beginning. If you have 2 Fe's at the beginning, you'll still have 2 Fe's at the end. 

Collision Theory


Source: https://www.youtube.com/watch?v=wbGgIfHsx-I

Inter vs. Intramolecular bonds

INTRA -- within (inside a particle <- think covalent bonds)
INTER -- between (felt between separate particles)


Notice, the H2O has intramolecular bonds and the Mg does not. The Mg is mixed with water but it is not bonded with intramolecular bonds.

Covalent Prefixes

 MEMORIZE these prefixes.



Lewis Dot Covalent - Methods

Method #1:


Method #2:
  1. Count the total number of electrons.
  2. Draw a structure with single bonds.
  3. Starting on the outside start adding dots in pairs so that each element is touching the appropriate number of electrons (H's = 2, all other elements = 8).
    COUNT AS YOU GO - remembering your goal from #1
  4. When you only have 4 electrons left - stop and look to see if you're going to run out. If you're going to run out start adding a double or a triple bonds with your final electrons.
  5. DOUBLE CHECK -- count to make sure everything is touching the appropriate number. Count to make sure you haven't gone over or below your total number from #1.
  6. Double check -- if you have multiple places where a double or triple bond could have gone - double check that you picked the right spot. What's the right spot?? IF elements have a choice they prefer to follow the "Step 5" rule. [ # of valence electrons + bonds = 8]. Sometimes atoms don't get a choice, but when they do they prefer a particular arrangement. Ex: Carbon Dioxide prefers a O=C=O instead of a single and triple bond.

Lewis Dot Ionic

Use families on the periodic table to identify how many valance electrons (represented by dots) each element has. 

Metals will LOSE electrons
and
Nonmetals will GAIN electrons

Metals lose all their valance electrons (they have other electrons in layers beneath), which nonmetals gain until they have 8 valance electrons. They ionically bond in whatever ratio is necessary for all the metals to lose electrons and all nonmetals to gain until they get to 8.